The present invention relates generally to air purification and, more particularly, to electronic air cleaners for use with residential and light commercial forced-air heating and/or cooling systems.
Conventional commercially available electronic air cleaners, such as for example the Model 31KAX electronic air cleaner formerly marketed by Carrier Corporation, typically comprise a plurality of ionizer wires, a plurality of collector plates and an associated power circuit for supplying high voltage DC power to the ionizer wires and the collector plates. The ionizer wires are typically tungsten wires that receive a positive charge from the power source. The collector plates comprise a series of spaced, parallel plates alternately charged positive and negative by the power source. The power circuit includes a transformer for converting standard 120 volt or 240 volt alternating current power to high voltage direct current power, for example about 6,000 vdc to 12,000 vdc.
In operation, particles, including for example household and atmospheric dust, lint, animal dander, food particles, tobacco smoke, aerosols, pollen, plant spores, and the like are ionized with a positive charge as the particles pass through the electrostatic field established by the ionizing wires. The charged particles thereafter are drawn to and deposited upon the negatively charged collector plates as the air flow in which the particles are entrained passes through the array of spaced, alternatively charged collector plates. Typically, a mechanical pre-filter is disposed upstream with respect to air flow of the ionizer wires to remove larger particles, for example particles having a mean diameter greater than 10 microns. The electrostatic cell portion of the air cleaner can remove particles as small as 0.01 microns in mean diameter.
While such conventional electrostatic precipitator type air cleaners are quite effective in trapping dust and other particles on the collector plates, if the plates are not cleaned regularly to remove the deposited particles, there may be potential for microbial growth on the particles on the collector plates. If microbial growth is present and is not removed through regular thorough cleaning, there is the possibility that bioaerosols such as fungal spores, bacteria and other allergens may be re-entrained into the air stream and circulated back into the occupied enclosure.
U.S. Pat. No. 3,744,216 discloses an air cleaner for purifying air in rooms of a home, office or other building. The disclosed air cleaner includes a mechanical particulate filter, a deodorizing filter, germicidal lamps and an electrostatically enhanced media filter. The germicidal lamps comprise a pair of ultraviolet lamps for irradiating the air upstream of the electrostatically enhanced media filter to kill bacteria, fungus spores, viruses and the like. The ultraviolet lights are disposed across from each other on opposite sides of the cleaner housing and are provided with shields so as to direct the ultraviolet rays towards each other across the path of the air flowing through the air cleaner so as to irradiate the airborne microbes. Bioaersols entrained in the air stream are exposed to the germicidal light from the lamps for only the short time that the air stream is passing between the lamps. This may not be sufficient time for the air stream to be sterilized before the air stream enters the media filter. As the germicidal light is not directed upon the media filter itself, bacterial growth may occur in the media filter and on the particulate collected in the filter.